For example, in an NC control apparatus of a working machine as shown in a patent document 1, a resonance frequency can be removed in a manner that, as shown in FIG. 7, a signal from a sweep signal generator (1 Hz to almost 100 Hz) 19 coupled to an adder is outputted as a positional command, then a frequency analyzer 20 detects the resonance frequency, and a cut-off frequency variable type notch filter 21 removes the resonance frequency.
According to an improved method of the aforesaid method, the apparatus is operated while sampling data such as a torque or a speed at every time period, then when a vibration detection portion detects a vibration having a pregiven magnitude, then the frequency of the sampled data is analyzed to obtain some frequencies having large frequency components, and a vibration suppression filter is set which cuts off frequencies or a frequency band equal to or larger than a given frequency with respect to frequencies having large vibration energy.
Thus method will be explained in detail with reference to a constitutional diagram shown in FIG. 5.
In FIG. 5, a reference numeral 1 depicts a servo control portion, 2 a vibration suppression filter, 3 a vibration detection portion, 4 a state variable trace portion, 5 a state variable frequency analysis portion, 8 a motor and 9 a machine to be controlled. The motor 8 includes a driver such as a current amplifier and a detector such as an encoder.
The servo control portion 1 receives a command from a not shown upper controller and controls a feedback signal from the motor 8 so as to follow the command thereby to operate the machine 9. The command received from the upper controller may be one of a positional command, a speed command and a torque command.
The control output from the servo control portion 1 is applied to the motor 8 as a command via the vibration suppression filter 2 having the frequency characteristics of decaying or a frequency band equal to or larger than a setting frequency.
The vibration detection portion 3 calculates a vibration level based on the feedback signal of the motor and the command to the motor and determines that the vibration is detected when the vibration level exceeds a threshold value set in advance.
The state variable trace portion 4 stores time histories the feedback signal of the motor, the command to the motor and values calculated based on them.
The state variable frequency analysis portion 5 analyzes the frequencies based on the data of the state variable trace portion 4 to calculate the vibration frequency.
The operation of the aforesaid configuration will be explained with reference to FIG. 6.
First, in step D1, the time histories such as the feedback signal of the motor are stored in the state variable trace portion 4 while performing the servo control.
In step D2, the vibration detection portion 3 calculates the vibration level, and determines that the vibration is detected when the vibration level exceeds the threshold value set in advance, whereby the process proceeds to step D3.
In step D3, the state variable frequency analysis portion 5 analyzes the frequencies based on the data of the state variable trace portion 4 to calculate the vibration spectrums of the respective frequencies, and outputs the frequency having a large spectrum or vibration energy, whereby the process proceeds to step D4.
In step D4, the frequency characteristics of the vibration suppression filter 2 is set based on the frequency obtained from the state variable frequency analysis portion 5. For example, when the vibration is due to the mechanical resonance, the vibration suppression filter is set to the configuration of a notch filter in which the obtained frequency has a selectively small gain, whereby the resonance characteristics can be effectively suppressed and controlled. According to the aforesaid method, the vibration suppression filter can be automatically set on-line.
Patent Document 1; Japanese Patent Unexamined Publication JP-A-05-346813 (FIG. 1)
Problem to be Solved
However, in the method of the related art, when the vibration suppression filter is set in the case where the accuracy of the frequency characteristics is bad or there are plural resonance frequencies, there is possibility that the vibration is excited or increased on the contrary.
Further, since the automatic setting starts when the vibration is detected on the way of the operation, it is difficult for an operator to stop the operation when the vibration increases.
Furthermore, since the frequencies are analyzed when the vibration is detected and then the vibration suppression filter is set, the vibration cannot be suppressed while the frequency is analyzed. Thus, when it takes a long time to analyze the frequencies, the machine may be damaged due to such a phenomenon that the amplitude of the vibration becomes too large before suppressing the vibration. In contrast, when the number of data for the frequency analysis is reduced in order to reduce the time required for the frequency analysis, the vibration may not be suppressed sufficiently due to such a fact that the frequency detection accuracy is degraded or the frequency detection range is narrowed.
Accordingly, an object of the invention is to provide a method of canceling a setting safely within an automatic setting sequence even in a case where a vibration suppression filter has an opposite effect. Alternatively, an object of the invention is to automatically set a setting frequency or a combination of setting frequencies where the vibration suppression filter works effectively in a case where there are plural resonance frequencies.
Further, an object of the invention is to provide a method of automatically setting a vibration suppression filter which can start the vibration suppression in a time as short as possible after the detection of the vibration and suppress the vibration with a sufficient accuracy.
Means to Solve the Problem
In order to attain the aforesaid object, according to a first aspect of the invention, there is provided a method of automatically setting a vibration suppression filter in a servo control apparatus which comprises:
a servo control portion for tracing a control system to a command;
the vibration suppression filter;
a vibration detection portion which measures a vibration level of the control system to detect a vibration;
a state variable trace portion for the control system; and
a state variable frequency analysis portion,
wherein when the vibration detection portion detects a vibration, the state variable frequency analysis portion analyzes frequencies of data from the state variable trace portion to calculate a vibration frequency, and frequency characteristics of the vibration suppression filter is set based on the vibration frequency,
the method of automatically setting the vibration suppression filter comprising:                storing a vibration level before an automatic setting of the vibration suppression filter to a vibration level store portion;        in a filter setting selection portion, comparing a vibration level after the automatic setting with the vibration level before the automatic setting; and        when the vibration level after the automatic setting is larger than the vibration level before the automatic setting, performing at least one of restoring of a setting of the vibration suppression filter to a state before the automatic setting and reducing a gain of the servo control portion.        
According to a second aspect of the invention, there is provided a method of automatically setting a vibration suppression filter in a servo control apparatus which comprises:
a servo control portion for tracing a control system to a command;
the vibration suppression filter;
a vibration detection portion which measures a vibration level of the control system to detect a vibration;
a state variable trace portion for the control system; and
a state variable frequency analysis portion,
wherein when the vibration detection portion detects a vibration, the state variable frequency analysis portion analyzes frequencies of data from the state variable trace portion to calculate a vibration frequency, and frequency characteristics of the vibration suppression filter is set based on the vibration frequency,
the method of automatically setting the vibration suppression filter comprising:
in the state variable frequency analysis portion, calculating a plurality of vibration frequency candidates,
based on the plurality of vibration frequency candidates and combinations thereof, sequentially setting the frequency characteristics of the vibration suppression filter and measuring and storing a vibration level; and
in a filter setting selection portion, determining a setting of the vibration suppression filter which is expected to have a smallest vibration level.
According to a third aspect of the invention, there is provided a method of automatically setting a vibration suppression filter in a servo control apparatus which comprises:
a servo control portion for tracing a control system to a command;
the vibration suppression filter;
a vibration detection portion which measures a vibration level of the control system to detect a vibration;
a state variable trace portion for the control system; and
a state variable frequency analysis portion,
wherein when the vibration detection portion detects a vibration, the state variable frequency analysis portion analyzes frequencies of data from the state variable trace portion to calculate a vibration frequency, and frequency characteristics of the vibration suppression filter is set based on the vibration frequency,
the method of automatically setting a vibration suppression filter comprising:
when a vibration is detected, first, setting the vibration suppression filter based on a result of the frequency analysis using a part of the data of the state variable trace portion; and
setting the vibration suppression filter based on a result of the frequency analysis using all of the data of the state variable trace portion.
According to a fourth aspect of the invention, there is provided an apparatus for automatically setting a vibration suppression filter for a servo control apparatus comprising:
a servo control portion for tracing a control system to a command,
the vibration suppression filter having frequency characteristics which decaying a component of frequencies or a frequency band equal to or larger than a setting frequency;
a vibration detection portion which calculates a vibration level based on a feedback signal of a motor and a command to the motor, and determines that a vibration is detected when the vibration level exceeds a threshold value set in advance;
a vibration level store portion which stores the calculation result of the vibration detection portion,
a state variable trace portion of the control system which stores the feedback signal of the motor, the command to the motor and time histories of values calculated based on them,
a state variable frequency analysis portion which analyzes frequencies based on the data of the state variable trace portion to calculate vibration frequencies, and
a filter setting selection portion which has a setting before an automatic setting of the vibration suppression filter and a setting of the automatic setting obtained by the frequency analysis, and switches between these settings,
wherein when the vibration detection portion detects a vibration, the state variable frequency analysis portion analyzes frequencies of the data of the state variable trace portion to calculate vibration frequency thereby to set frequency characteristics of the vibration suppression filter based on the calculated vibration frequency,
the vibration level store portion stores a vibration level before the automatic setting of the vibration suppression filter,
the filter setting selection portion compares a vibration level after the automatic setting with the vibration level before the automatic setting stored in the vibration level store portion, and
when the vibration level after the automatic setting is larger than the vibration level before the automatic setting, at least one of restoring of a setting of the vibration suppression filter to a state before the automatic setting and reducing of a gain of the servo control portion is performed.
According to a fifth aspect of the invention, there is provided an apparatus for automatically setting a vibration suppression filter for a servo control apparatus, comprising:
a servo control portion for tracing a control system to a command;
the vibration suppression filter having frequency characteristics which decaying a component of frequencies or a frequency band equal to or larger than a setting frequency;
a vibration detection portion which calculates a vibration level based on a feedback signal of a motor and a command to the motor and determines that a vibration is detected when the vibration level exceeds a threshold value set in advance;
a vibration level store portion which stores the calculation result of the vibration detection portion;
a state variable trace portion of the control system which stores the feedback signal of the motor, the command to the motor and time histories of values calculated based on them;
a state variable frequency analysis portion which calculates a plurality of vibration frequency candidates; and
a filter setting selection portion which has settings of automatic settings obtained by analysis of the plural frequencies of the vibration suppression filter, and switches between these settings,
wherein when the vibration detection portion detects a vibration, the state variable frequency analysis portion analyzes frequencies of the data of the state variable trace portion to calculate vibration frequency thereby to set frequency characteristics of the vibration suppression filter based on the calculated vibration frequency,
the state variable frequency analysis portion sequentially sets the frequency characteristics of the vibration suppression filter based on the plurality of vibration frequency candidates and combinations thereof and thereafter measures and stores a vibration level, and
the filter setting selection portion determines a setting of the vibration suppression filter which is expected to have a smallest vibration level.
According to a sixth aspect of the invention, there is provided an apparatus for automatically setting a vibration suppression filter for a servo control apparatus, comprises:
a servo control portion for tracing a control system to a command;
the vibration suppression filter having frequency characteristics which decaying a component of frequencies or a frequency band equal to or larger than a setting frequency;
a vibration detection portion which calculates a vibration level based on a feedback signal of a motor and a command to the motor and determines that a vibration is detected when the vibration level exceeds a threshold value set in advance;
a vibration level store portion which stores the calculation result of the vibration detection portion;
a state variable trace portion of the control system which stores the feedback signal of the motor, the command to the motor and time histories of values calculated based on them;
a state variable frequency analysis portion which analyzes frequencies based on the data of the state variable trace portion to calculate vibration frequencies; and
a filter setting selection portion which sets the vibration suppression filter based on a calculated result of the state variable frequency analysis portion,
wherein when the vibration detection portion detects a vibration, the state variable frequency analysis portion analyzes frequencies of the data of the state variable trace portion to calculate vibration frequency thereby to set frequency characteristics of the vibration suppression filter based on the calculated vibration frequency,
after the vibration detection portion detects a vibration, first, the state variable frequency analysis portion analyzes the frequencies based on a part of data of the state variable trace portion,
then the filter setting selection portion sets the vibration suppression filter based on a result of the frequency analysis,
then the state variable frequency analysis portion analyzes the frequencies based on all data of the state variable trace portion, and
then the filter setting selection portion sets the vibration suppression filter based on a result of the analysis using all of the data of the state variable trace portion.
Advantage of the Invention
According to the first and fourth aspects of the invention, even when the vibration becomes large due to the automatic setting of the vibration suppression filter, the setting is restored automatically and quickly and so the enlargement of the vibration can be prevented. Alternatively, the vibration can be suppressed by reducing the control gain.
Further, according to the second and fifth aspects of the invention, even when there are two or more resonance frequencies of the machine, an effective filter setting can be found automatically. Furthermore, even if a vibration frequency not originally existing in the machine arises within the calculation of the frequency analysis, since the setting is not employed, only the effective filter setting can be employed.
Furthermore, according to the third and fifth aspects of the invention, after detecting the vibration, first, the vibration suppression filer is set based on a result of the frequency analysis according to a method using a part of the data which is not complete in the accuracy but can calculate at a high speed, whereby the abrupt divergence of vibration can be prevented. Further, the vibration suppression filer is set again based on a result of the frequency analysis according to a method using all of the data which takes a long calculation time but is highly accurate, the frequency can be obtained surely and the vibration can be suppressed.